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## HUMAN POPULATION DYNAMICS

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**See World Population Video**Video • What do you think? Did you Know?**How many people are on Earth?**• 6,788,977,211 (6.8 billion) • How many people are in the U.S.? • 308 million • How much is 6.8 billion? • See next slide for an exercise Pop Census**How long would it take you to put 6.8 billion dots on a**piece of paper? • Take out a piece of paper and pen or pencil. • Count the number of dots you can put on a piece of paper in 5 seconds (have a partner time 5 sec). • Calculate Dots/minute (x12), dots/hour (x60), dots/day (x24), dots/year (x365). • 6.8 billion dots divided by dots/year Note: 77 million more people added per year you were putting dots**How many people are on Earth?**• How much is one billion? • How long is 7.8 billion seconds? • 1 billion seconds is 31 years, 8.5 months! • 6.8 billion = 215 years, 7.5 months!**History of Human Pop Growth**• 1804: 1 billion (took a looong time) • 1927: 2 billion (took 123 years more) • 1960: 3 billion (33 years) • 1974: 4 billion (14 years) • 1987: 5 billion (13 years) • 1999: 6 billion (12 years) • ????: 7 billion (? Years)**World Clock**Current Pop Growth Rate In these 10 seconds… • 10 • 9 • 8 • 7 • 6 • 5 • 4 • 3 • 2 • 1 • 0 • 41 people were born • 18 people died • = 23 people added to Earth During this class… 39,244 born; 17,187 died; 22,058 people added**Current Pop Growth Rate**• 1.15% annual growth • What does this mean? • Use Rule of 70 to determine Doubling Time**Type of Pop Growth**• Exponential Growth: J Curve • Occurs when pop is growing at a percent annual growth (versus some fixed amount).**Power of exponential growth:paper folding example**# Folds Thickness 10 3.9 inches 20 332 feet 30 64 miles 40 65,943 miles 50 67.5 million miles Using 0.0038” for paper thickness (20 lb test) = 263 sheets/inch.**Rule of 70 to determine Doubling Time**• 70 divided by % Annual Growth = Doubling Time (i.e., how long it takes for the population to double)**Rule of 70: Example 1**• Example: 10% annual growth rate • Current population is 1 million • How long will it take to reach: • 2 million? • 70/10 = 7 years • 8 million? • 7 X 3 doubles = 21 years**Rule of 70: Example 2**• Example: 1.15% annual growth rate • Answer: 70/1.2 = 61 years for population to double in size • So… in 61 years, at this rate, we will have twice as many people on Earth!**Exponential Growth**What should be done? http://dieoff.org/page80.htm**Exponential Growth**What should be done? http://dieoff.org/page80.htm**Exponential Growth**What should have been done? http://dieoff.org/page80.htm**Exponential Growth**What should wildlife managers do? Hunt themAdd predatorsMove themDo nothing (let them starve)**Here’s another population**What did you say we should do?**Biotic Potential vs. Environmental Resistance**• One pair of cats adds up to (assumes no deaths): • First yr: 12 • Second yr: 66 • Third yr: 382 • Fourth yr: 2201 • Tenth yr: 80,399,780**Carrying Capacity**• MAXIMUM number of individuals an area can support FOREVER. • Law: Thou shalt not exceed the carrying capacity, for long. • As the caribou found out**Carrying Capacity**• What is the carrying capacity for people on Earth?**Cultural Carrying Capacity**• Maximum number of individuals an area can support forever AT A GIVEN STANDARD OF LIVING. OR**What determines whether a population size changes?**• Rate of Increase = (Birth Rate +Immigration) – (Death Rate + Emigration) • Age Structure =age and sex proportions in a population • Total Fertility Rate = average # of children a woman has in her lifetime. • Replacement Level Fertility Rate = average # of children a couple must have to replace themselves. • 2.1 in MDCs and 2.5 in LDCs**AGE STRUCTURE**Fig. 4.8**Factors affecting birth rates**• Education • Affluence • Religious/cultural norms • Role of women in society • Infant mortality rates • Availability of birth control**What determines whether a population size changes?**• Life Expectancy = how long an individual • is expected to live once they are born.**What determines whether a population size changes?**• Life Expectancy = how long an individual • is expected to live once they are born. • WHAT FACTORS DO YOU THINK • INFLUENCE LIFE EXPECTANCY?**Human Population Growth and the Environment**• Who has a greater impact on the environment? • Lesser Developed Countries?? • More Developed Countries??**Two Types of Overpopulation**• People Overpopulation • Consumption Overpopulation • Who has greater impact on the environment – Lesser Developed Countries with 80% of the people or More Developed Countries using high percentage of the resources?**Questions**• How does population growth affect our world today? • What will happen in the future if we do not control population? • What are the options for controlling population? Pros and Cons: • Volunteer vs Forced • How should we control population?**If we could shrink the earth's population to a village of**precisely 100 people,with all the existing human ratio's remaining the same, there would be: • 57 Asians • 21 Europeans • 14 from the Western Hemisphere, both N and S • 8 Africans • 52 would be female • 48 would be male • 70 would be nonwhite • 30 would be white**If we could shrink the earth's population to a village of**precisely 100 people,with all the existing human ratio's remaining the same, there would be: • 70 would be non-Christian • 30 would be Christian • 6 people would possess 59% of the entire world's wealth and • all 6 would be from the United States